1. Field of the Invention
The present invention relates to a cold cathode ionization vacuum gauge and an auxiliary electrode used therefor. In particular, it relates to a cold cathode ionization vacuum gauge of the inverted magnetron type.
2. Related Background Art
A cold cathode ionization vacuum gauge measures the pressure of a gas by inducing ionization of the gas by self-discharge at the anode and the cathode. Known conventional cold cathode ionization vacuum gauges include the penning type, the magnetron type, and the inverted magnetron type (see Japanese Patent Application Laid-Open No. H10-19711, for example). In particular, the magnetron type and the inverted magnetron type are suitable for measurement of high vacuum because of their high electron trap efficiency and the configuration that allows stable sustained discharge even in a high vacuum area.
In order for a cold cathode ionization vacuum gauge to start discharge, a high voltage needs to be applied to induce ionization. However, a time lag occurs at the boundary between the period in which the high voltage is applied to the cold cathode ionization vacuum gauge and the period in which sustained discharge occurs and a discharge current flows. The time lag affects the time of start of measurement.
As a solution to this problem, Japanese Patent Application Laid-Open No. H6-26967 discloses that discharge inducing means that directly applies a sufficient amount of electromagnetic radiation to cause a cathode to emit photoelectrons is provided on the cathode. Japanese Patent Application Laid-Open No. H6-26967 discloses a cold cathode ionization vacuum gauge of the inverted magnetron type for which the discharge induction time between the application of a high voltage and the start of sustained discharge can be reduced.